Agglomerating process and apparatus



Sept. 8, 1970 J. HAGER AGGLOMERATING PROCESS AND APPARATUS Filed Feb. 23, 1967 VVf/llll/fl/f INVENTOR. JOHN L. HAGER BY W United States Patent 3,527,647 AGGLOMERATING PROCESS AND APPARATUS John L. Hager, Northfield, Minn., assignor to Northfield Processed Food Systems Company, Inc., Northfield, Minn., a corporation of Minnesota Filed Feb. 23, 1967, Ser. No. 617,997 Int. Cl. A230 9/00; A231 1/00; A21d 6/00 US. Cl. 99-199 9 Claims ABSTRACT OF THE DISCLOSURE A flat spray of air-atomized liquid of controlled concentration, such as water at 35l55 F., is directed from an orifice downwardly at an acute angle onto a moving surface such as an imperforate, metallic conveyor belt. The powdered material is fed downwardly onto the spray close to the orifice so that the agglomerates are deposited as an extended layer on the belt which may be heated to effect drying.

BACKGROUND OF THE INVENTION This invention relates to the art of agglomerating whereby certain powdered materials of the type which become tacky when superficially moistened are converted into agglomerates which have a lower bulk density than the powdered material and may be dissolved or dispersed more readily than the unagglomerated material. More particularly, the invention relates to an improved method and apparatus for agglomerating powdered material.

Under prior art practices, powdered materials have been agglomerated by directing a moistening agent, such as wet steam, onto a falling stream or dispersed cloud of the material. In order to effect agglomeration of substantially all particles of the powdered material, it is necessary to employ substantial amounts of moisture so that the resulting agglomerates are quite moist and hence must be subjected to considerable heat in a drying operation. The application of such high heat may have a deleterious effect upon the flavor, color or texture of certain materials such as food products, for example. The prior art use of high temperature moistening fluids, such as steam, is also objectionable because it heats the particles of powdered material and so retards the condensation of moisture on the particles. Another disadvantage of certain prior art practices is due to the failure to moisten the finer particles of the powdered material so that the unmoistened particles do not form agglomerates but are air-borne and hence must be drawn out of the agglomerating chamber by an exhaust fan and re-circulated in the system. The agglomerating apparatus of the prior art is generally quite complicated, bulky and expensive. The cost of operating the prior art apparatus is relatively expensive since the drying equipment, fines re-circulating system and the like require substantial amounts of heat and power. Prior art practices which use steam as a moistening agent for agglomerating food products, for example, require special care and/ or equipment for generating steam which must be free from contaminating substances.

SUMMARY OF THE INVENTION Objects of the present invention are to provide agglomerating process and apparatus which will overcome the aforementioned disadvantages of the prior art. In accordance with the present invention, a stream of powdered material to be agglomerated flows downwardly onto the top of a substantially flat spray of air-atomized moistening liquid, such as water at a temperature of 35-155 F. The spray is directed downwardly at an acute angle onto a moving surface such as an imperforate metallic conveyor belt, for example. The powder to be agglomerated is fed downwardly onto the spray with the stream of material 'ice confined substantially to an area located adjacent to the orifice from which the spray is emitted and between and contiguous to the diverging side boundaries of the spray. As the powder is deposited in this area it is scattered with a sudden violence and driven downwardly against the imperforate moving surface so that substantially all of the particles of powder are moistened. Some agglomerates are formed by random collision of moistened particles and fall onto the moving surface while other agglomerates are formed, or if already formed may be enlarged by forcibly directing moistened particles and/ or agglomerates against the imperforate surface upon which all agglomerates are deposited as an extended layer. The imperforate surface, such as a metallic conveyor belt, may be heated if an after-drying operation is required.

In the practice of the invention, substantially all particles of the powdered material are moistened and agglomerated and hence there are no air-borne finer particles (fines) to be removed from the agglomerating zone. Potable water which enters the nozzle at a temperature of about 35 -155 F. provides a readily available and relatively economical moistening agent. The concentration of the air-atomized liquid can be selectively controlled so that agglomeration of all particles of the powdered material can be effected with the application of a minimum amount of moistening liquid. Hence, very little, if any, after-drying of the agglomerates is required. The apparatus of the invention is relatively simple and compact in structure and economical in operation when compared to the complicated, bulky prior art apparatus which includes such equipment as steam generators, cyclones, exhaust systems for re-circulating the fines, extensive after-drying equipment and the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of one form of the apparatus embodying the invention and suitable for carrying out the improved process.

FIG. 2 is a fragmentary perspective view showing the method of feeding powdered material into the spray.

FIG. 3 is sectional view, on an enlarged scale, taken on line 3-3 of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS A preferred embodiment of the invention which has been used successfuly in practicing the invention comprises the hopper 10 from which the powdered material to be agglomerated is fed continuously into the electrically vibrated feeder 11 and thence downwardly through the spout 12 onto the atomized spray of moistening liquid indicated at 13. The air-atomized moistening liquid, such as water, is discharged as a substantially flat, sheet-like spray which diverges from the slotted orifice 14 formed in nozzle 15.

Filtered compressed air is directed into nozzle 15 by air conduit 16 with the pressure controlled selectively by means of the valve 17 and gage 18. Moistening liquid, such as potable water from the city mains, is supplied to the nozzle 15 by water conduit 19 with the pressure of the liquid controlled by valve 20 and the gage 21. In one successful embodiment of the invention, the nozzle 15 or spray set-up comprises the Spraying Systems Co. fluid nozzle No. 1650 having a central fluid aperture 0.016 inch in diameter and 3 encircling air apertures with diameters of 0.09375 inch and air nozzle No. 73420 having a slotted orifice 0.070 inch high and 0.375 inch wide to provide a fiat, sheet-like spray of atomized liquid.

As shown in FIG. 2, the powdered material is fed downwardly from spout 12 in a relatively concentrated stream onto the spray 13. The stream of material is confined so that it falls substantially on an area of the spray, indicated at 22, which is closely adjacent the orifice 14 and is located between and is contiguous to the diverging side boundaries 23 and 24 of the spray 13. The curved lower end of spout 12 is located about one inch above and about one-half inch forwardly of the orifice 14 so that the powdered material contacts the spray 13 with very little acceleration. As the powdered material makes contact with the spray, it is subjected to a violent action which effects a mositening of substantially all of the particles and projects them into a zone of turbulence where the tacky particles collide in random manner and form agglomerates.

The nozzle 15 is inclined downwardly at an acute angle with the horizontal so that the spray 13 is directed downwardly onto a substantially horizontal moving surface such as the imperforate, flexible steel conveyor belt which is mounted to move, in the direction of the arrow, on pulleys 26 and 27 and positioned forwardly of and be low the nozzle 15. The force of the spray 13 drives the agglomerates onto the upper surface of belt 25 and also drives wetted particles and agglomerates into contact with other wetted particles and agglomerates to form larger agglomerates. The agglomerating action is thereby promoted because the particles and agglomerates are forcibly contacted by being driven against other particles and agglomerates which have been deposited on the imperforate surface of belt 25. Since the belt 25 is moving during the agglomerating action, the agglomerates are deposited on the belt 25 as an extended layer 28 which remains quiescent until removed by the doctor blade 29 so that the agglomerates fiow down chute 30 into container 31.

The concentration of moisture in the spray, i.e. the size of the droplets, can be selectively controlled by varying the relative air and liquid pressures by means of the valves and gages. Optimum results have been obtained by employing air pressure which is from 2 to 30 times greater than the water pressure. For a given liquid pressure an increase in the air pressure will produce a decrease in the droplet size of the spray. By varying the droplet size in the spray, it is possible to effect successful agglomeration of various types of powdered materials with a minimum amount of moisture. Thus, for materials which run to the finer particle size a spray with the finer droplet sizes is used and for materials with the coarser particle size a spray with larger droplets is used. Since agglomeration is effected with a minimum amount of moisture, the agglomerates require little, if any, after-drying. Various kinds of powdered materials have been agglomerated successfully in an operation wherein the agglomerates were deposited on belt 25 while it was at normal room temperature.

However, if additional heat is required for an after-drying operation on the agglomerates, this can be provided conveniently by means of a water pan 32 positioned beneath and closely adjacent to the under side of the upper part of belt 25. Hot water from a suitable source can be directed into the pan 32 and re-circulated by means of conduits 33, 34 and pump 35 to heat the belt 25 to a desired temperature for drying the agglomerates. Drying of the layer of agglomerates 28 may also be effected by circulating warm air through a hood 36 which may be installed over the belt 25 as shown on the drawing.

The invention has been embodied and practiced successfully with an apparatus in which the endless belt 25 is formed of imperforate, flexible, stainless steel with a polished outer surface for receiving the layer of agglomerates. The belt 25 is 19 inches wide and is mounted on pulleys which are spaced about 12 feet from center to center. The nozzle 15, with dimensions and construction hereinbefore stated, is mounted about 4-6 inches above one end of the belt 25 as shown in FIG. 1. The nozzle 15 is downwardly inclined at an acute angle of 12-35 from the horizontal so that the spray is directed downwardly onto belt 25 at about 8-14 inches forwardly of the nozzle. The spout 12 is about one inch is diameter and the powdered material is fed downwardly in 'the spout 12 so that a stream of material about 0.5-1.0 inch wide and about 0.125-0.375 inch in thickness falls onto the spray at area 4 22 which is located about 0.51.0 inch forwardly of the orifice 14. With apparatus of the type described various kinds of powdered materials were agglomerated successfully as described in the following examples.

Example I Powdered material in the form of conventional non-fat, dried milk solids, having a moisture content of 4.0% and a bulk density of 0.68 g./cc., were placed in hopper 10 and fed downwardly into spray 13 at the rate of lbs. per hour. The nozzle was directed downwardly toward the top of belt 25 at an angle of about 15 and filtered air under a pressure of 30 psi. was directed into the nozzle. Water from city mains which had been heated to about 150 F. was directed into the nozzle at a pressure of 1 psi. The agglomerates were formed as a layer about one-eighth inch thick on the top of the belt 25 which was at a room temperature of 70 F. and moving at the rate of 15 feet per minute so that the agglomerates remained on the belt for about 48 seconds. The resulting agglomerates had a bulk density of 0.24 g./cc. and a moisture content of 4.4% When 50 cc. of the agglomerates were placed on the surface of 100 cc. of water in a beaker at 50 F., all of the agglomerates dropped below the surface in 30 seconds. For comparison in a similar dispersion test, unagglomerated powder dropped below the water surface in 30 minutes.

Agglomerates were also formed with the same material and under the same operating conditions excepting that the belt 25 was heated to F. to provide an after-drying action on the agglomerates. The resulting agglomerates had a bulk density of 0.24 g./cc. and a moisture content of 3.2% and when placed on the surface of water at 50 F. substantially all dropped below the surface in 10 seconds.

Agglomerates were formed with the same material and under the same operating conditions as in the next preceding paragraph excepting that the water was directed into the nozzle 15 at a temperature of 55 F. The resulting agglomerates had a bulk density of 0.33 g./cc. and a moisture content of 3.6% and when placed on a water surface dropped below the surface in 10 seconds.

Example II Dried whole milk powder with 28% butterfat and having a bulk density of 0.55 g./cc. and a moisture content of 2.8% was agglomerated under the conditions of Example I with the water at F. and the belt 25 at 70 F. The resulting agglomerates had a bulk density of 0.48 g./cc. and a moisture content of 3.4%. When placed on the sunface of water at 100 F. substantially all agglomcrates dropped below the surface in 30 seconds. In a similar dispersion test for comparison with the same material in unagglomerated form, 4 minutes elapsed before substantially all material dropped below the surface.

Agglomerates were also formed with the same material and under the same operating conditions excepting that the belt 25 was heated to 140 F. The resulting agglomerates had a bulk density of 0.48 g./cc. and a moisture content of 3.2% and when placed on a water surface at 100 F. substantially all dropped below the surface in 15 seconds.

Agglomerates were formed with the same material and under the same operating conditions as in the next preceding paragraph excepting that the water was directed into the nozzle 15 at a temperature of 55 F. The resulting agglomerates had a bulk density of 0.37 g./cc. and a moisture content of 2.6% and when the dispersion test was made substantially all dropped below the surface in 30 seconds with slight agitation.

Example III A dessert mix consisting of 12% gelatin, 86% sugar and 2% other ingredients and having a bulk density of 0.69 g./cc. and 3.0% moisture was agglomerated under the conditions described in Example I with the belt at 70 F. and water entering the nozzle at 150 F. The resulting agglomerates had a bulk density of 0.39 g./cc. and a moisture content of 3.5%; and when placed on the surface of water at 50 F. substantially all dropped below the surface in 10 seconds. By comparison, about 30 minutes elapsed before the unagglomerated material dropped below the surface.

Agglomerates were also formed with the same material and under the same operating conditions excepting that belt 25 was heated to 140 F. The resulting agglomerates had a bulk density of 0.39 g./cc. and a moisture content of 2.8%; and when placed on the surface of water at 50 F. substantially all dropped below the surface in seconds.

Other agglomerates were formed with the same material and operating conditions in the next preceding paragraph excepting that the water was directed into nozzle 15 at a temperature of 55 F. The agglomerates had a bulk density of 0.45 g./cc. and a moisture content of 2.8%;

and when placed on water at 50 F. dropped below the surface within 2 seconds.

Example IV Wheat flour having a bulk density of 0.59 g./cc. and a moisture content of 6.2% was agglomerated under the operating conditions described in Example I with the belt at 70 F. and water entering the nozzle 15 at 150 F. The resulting agglomerates had a bulk density of 0.43 g./ cc. and a moisture content of 6.9%. When placed on the surface of water at 100 F. substantially all agglomerates dropped below the surface in 30 seconds whereas the unagglomerated flour required about 6 minutes to drop below the water surface.

Agglomerates were formed with the same material and under the same conditions excepting that the belt 25 was heated to 140 F. The resulting agglomerates had a 'bulk density of 0.42 g./cc. and a moisture content of 3.8%; when placed on the surface of water at 100 F. substantially all dropped below the surface in 10 seconds.

Agglomerates were also formed with the same material and under the same operating conditions described in the next preceding paragraph excepting that the water entered the nozzle at 55 F. The agglomerates had a bulk density of 0.54 g./ cc. and a moisture content of 4%; and when placed on the surface of water at 100 F. substantially all dropped below the surface in 10 seconds with slight mixing.

The moisture content of the agglomerates may, if desired, be further reduced by circulating warm. air through the hood 36 positioned over the top of belt 25 as shown on the drawings. Thus, the agglomerates of the non-fat milk solids in Example I have a moisure content of 4.4% when processed with the belt 25 at 70 F. and a moisture content of 3.2% when processed with the belt 25 at 140 F. If desired, the moisture content of the agglomerates may be further reduced to 2.9% by additional drying action provided by circulating air at 180 F. and at the rate of 500 cubic feet per minute through the hood 36 positioned over belt 25 which is heated to 140 F.

In the foregoing examples, agglomeration was effected with air atomized water produced by dirceting air fected with air atomized water produced by directing air into the nozzle at 30 p.s.i. and water at 1 p.s.i. This relation of air and water pressures provides a spray having very small droplet size so that the powdered material is agglomerated with a minimum of moisture. If, for example, the air pressure is maintained at 30 p.s.i. and the water pressure is increased to 10 p.s.i., a spray with larger droplet size will be produced so that more moisture will be added to the agglomerates. Thus, a gelatin dessert mix having a bulk density of 0.70 g./ cc. and a moisture content of 3% was agglomerated by using the belt at 140 F., water at 50 F. under 1 p.s.i. and air at p.s.i. The resulting agglomerates had a bulk density of 0.49 g./cc. and a moisture content of 2%. The process was repeated with the same material and under the same conditions excepting that the water pressure was increased to 10 p.s.i. The resulting agglomerates had a bulk density of 0.24 g./cc. and a moisture content of 3.2%.

Although in the preferred embodiment the belt 25 is imperforate and metallic, the agglomerating process has been carried out by employing a conveyor belt 25 which was made of a 55-mesh metallic screen material. While a single nozzle and associated feeder spout has been described, capacity for producing agglomerates may be increased by arranging a plurality of laterally spaced nozzles and associated feeders to deposit a layer of a'gglomerates on a belt of suitable width. The process may also be practiced with the belt 25 formed of imperforate rub ber-like material such as is widely used in the food industry.

I claim:

1. A process of forming agglomerates comprising: supplying liquid water to a water atomizing nozzle rneans, discharging said liquid water from said nozzle means as a diverging, substantially fiat, sheet-like, atomized spray directed downwardly onto a moving surface at an acute angle therewith; feeding a confined, relatively concentrated stream of powdered material downwardly into the diverging, atomized spray between and contiguous to the diverging side boundaries thereof from a location adjacent to said nozzle means and forwardly thereof thereby moistening the particles; the force of the atomized spray scattering the moistened particles driving them into random collision thereby forming agglomerates and projecting the formed agglomerates onto the moving surface as an extended layer; allowing the agglomerates on the moving surface to dry as a quiescent extended layer; and removing said agglomerates from said surface.

2. The process defined in claim 1 including the step of maintaining the layer of agglomerates substantially quiescent while it undergoes drying action on the moving surface which is imperforate and metallic.

3. The process defined in claim 1 wherein the water is supplied at a temperature of 35 155 F.

4. The process defined in claim 1 including the step of maintaining the layer of agglomerates quiescent while subjecting it to drying action by heating to a temperature of -180 F.

5. The process defined in claim 1 wherein the water is atomized by air and water under respectively different pressures and including the step of controlling the moisture concentration of the spray by varying the air pressure so that it is from 2 to 30 times greater than the water pressure.

6. The process in accordance with claim 1 wherein the moving surface is formed of imperforate metal which is heated to a temperature of 100-180 F.

7. The process in accordance with claim 1 including the steps of directing the spray downwardly at an acute angle with the horizontal and onto a horizontal imperforate moving surface, feeding the powdered material downwardly onto the spray at an area which is from 0.5- 1.0 inch forwardly of the nozzle to form the agglomerates which are deposited as an extended layer on said moving surface.

-8. Apparatus for producing agglomerates of powdered materials of the type which become tacky when moistened including, means for feeding the powdered material into a spray of moistening liquid discharging from an orifice means wherein the improvement comprises means for air atomizing a liquid and discharging it from said orifice means as a diverging, substantially flat, sheet-like atomized spray, inclined downwardly at an acute angle to the horizontal, means for feeding a confined, relatively concentrated stream of the powdered material downwardly on top of the spray between and contiguous to the diverging side boundaries thereof from a location adjacent to said nozzle means and forwardly thereof to thereby moisten substantially all the particles of material 7 8 and tumble them in a zone of turbulence to form agglom- 2,949,363 8/1960 Bissell 99-56 crates, and a substantially horizontal moving surface be- 2,957,771 10/1960 Prater et a1. 99140 low and forwardly of the orifice for receiving the agglom- 2,977,203 3/1961 Sienkiewicz et a1. 23313 erates. 3,143,428 8/ 1964 Rcimers et al. 99141 9. Apparatus in accordance with claim 8 in which the 5 moving surface is an endless metallic conveyor belt LIONEL M. SHAPIRO, Primary Examiner mounted between pulleys and further comprises means W C LAWTON Assistant Examiner for heating the surface.

References Cited UNITED STATES PATENTS 2,832,686 4/1958 Louder et al. 9956 .U.S. c1. X.R. 99-56, 93, 234; 23 313; 264-117 

